CO2 in Arctic snow cover: landscape form, in-pack gas concentration gradients, and the implications for the estimation of gaseous fluxes

The physical characteristics and CO2 concentrations of snow cover in the we stern Canadian arctic were examined at sites with different landscape forms (valley floor, hillslope, plateau). The greater exposure of plateau snow c over to blowing snow results in differences in the structure of the snow co ver and different snow strata compared with snow covers on the other landsc ape forms. Both higher in-pack concentrations of CO2 and the largest vertic al CO2 concentration gradients were found in plateau snow cover, the smalle st in the deeper hillslope and valley snows. CO2 gradients in all landscape snow covers followed two patterns, i.e. where concentrations at the soil-s now interface are higher than those just below (5 cm) and the snow-atmosphe re interface and vice versa. The latter pattern is due to the transport of the gas from the lower levels to the upper levels of the snowpack by wind-i nduced advection (windpumping) and is indicative of non steady-state, nondi ffusive processes. These latter processes should thus be considered in any studies on CO2 fluxes from Arctic soil where snow cover topography and wind s are conducive to windpumping and where concentration gradients resulting from diffusive processes have not been clearly identified. Copyright (C) 19 99 John Wiley & Sons, Ltd.